CN114406011B - Hot rolling process for low-carbon high-sulfur free-cutting narrow strip steel - Google Patents
Hot rolling process for low-carbon high-sulfur free-cutting narrow strip steel Download PDFInfo
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- CN114406011B CN114406011B CN202210020684.6A CN202210020684A CN114406011B CN 114406011 B CN114406011 B CN 114406011B CN 202210020684 A CN202210020684 A CN 202210020684A CN 114406011 B CN114406011 B CN 114406011B
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 66
- 239000010959 steel Substances 0.000 title claims abstract description 66
- 229910052717 sulfur Inorganic materials 0.000 title claims abstract description 44
- 239000011593 sulfur Substances 0.000 title claims abstract description 43
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 38
- 238000005520 cutting process Methods 0.000 title claims abstract description 30
- 238000005098 hot rolling Methods 0.000 title claims abstract description 24
- 238000005096 rolling process Methods 0.000 claims abstract description 133
- 238000010438 heat treatment Methods 0.000 claims abstract description 112
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 19
- 239000001301 oxygen Substances 0.000 claims abstract description 19
- 238000004321 preservation Methods 0.000 claims abstract description 13
- 238000005336 cracking Methods 0.000 claims abstract description 12
- 229910000915 Free machining steel Inorganic materials 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 5
- 239000000779 smoke Substances 0.000 claims abstract description 4
- 238000002791 soaking Methods 0.000 claims description 22
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 14
- 239000003546 flue gas Substances 0.000 claims description 14
- 239000000498 cooling water Substances 0.000 claims description 12
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 238000000926 separation method Methods 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 11
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- CADICXFYUNYKGD-UHFFFAOYSA-N sulfanylidenemanganese Chemical compound [Mn]=S CADICXFYUNYKGD-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/48—Tension control; Compression control
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/004—Heating the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
Abstract
The invention discloses a low-carbon high-sulfur free-cutting narrow strip steel hot rolling process which comprises the steps of billet heating time control, heating temperature control, cooling, heat preservation, temperature raising, smoke residual oxygen control, steel rolling temperature control, pass reduction control, edge temperature drop control and finish rolling temperature control. After the low-carbon high-sulfur free-cutting steel heating process and the rolling process control method are implemented, the problems of hole type slip steel clamping, head separation, finished product edge cracking and the like can be effectively prevented, and the phenomena of hole type slip steel clamping and rolling cracking of a rolling mill in the production process are avoided.
Description
Technical Field
The invention relates to a hot rolling control method, in particular to a hot rolling process of low-carbon high-sulfur free-cutting narrow strip steel.
Background
The low-carbon high-sulfur free-cutting narrow strip steel is mainly used for stamping a key blank for manufacturing a high-grade key after cold rolling, has higher sulfur and phosphorus content and has excellent cutting performance. Because of the characteristics of elements such as high sulfur and phosphorus, the hot rolling difficulty is high. Before the company develops the low-carbon high-sulfur free-cutting narrow strip steel (the main component ranges of C is 0.05-0.09%, mn is 1.1-1.5%, si is 0.015-0.08%, S is 0.35-0.42% and P is 0.04-0.09%), the domestic free-cutting narrow strip steel for keys is mainly imported material. The research and technical literature of low-carbon high-sulfur free-cutting smelting are relatively more, the rod and wire rod production of main users is realized, the successful mass production of the hot-rolled narrow strip steel is less, and the research on the control of the hot-rolled production process of the low-carbon high-sulfur free-cutting narrow strip steel is relatively less.
The difference between the narrow strip steel rolling and the line and bar rolling is larger, firstly, the thickness of the finished narrow strip steel is thinner, the thickness of the low-carbon high-sulfur free-cutting narrow strip steel is generally 2.5-4.0mm, and the temperature drop in the rolling process is quick, especially the temperature drop of the edge part is quick, so that the plasticity of the edge part is poor, and the edge part cracking phenomenon is extremely easy to occur in the rolling extension process. Secondly, the narrow strip steel is subjected to flat rolling, rough rolling is a box-shaped hole, the contact of the hole type and the steel billet is mainly the contact of the upper surface and the lower surface, the rough rolling red billet is thicker, the low-carbon high-sulfur free-cutting steel has high sulfur content and low carbon and silicon content, the friction coefficient is small, and the hole type slipping and steel clamping phenomenon of the rough rolling hole type is easy to occur in the rolling process. In addition, the high hot brittleness of sulfur and low rolling temperature can cause the phenomenon of cracking of the rolling process. The low-carbon high-sulfur free-cutting narrow strip steel has higher heating requirement on the blank, reduces the pass pressure rate and the edge temperature in the hot rolling process, and effectively controls the temperature range in the rolling process. The control of the proper heating process and rolling process is the key to the production of the low-carbon high-sulfur free-cutting narrow strip steel.
Disclosure of Invention
The invention aims to: the invention aims to provide a low-carbon high-sulfur free-cutting narrow strip steel hot rolling process for preventing hole type slip from clamping steel, leading head to separate layers and cracking of the edge of a finished product.
The technical scheme is as follows: the invention relates to a hot rolling process of low-carbon high-sulfur free-cutting narrow strip steel, which comprises the following steps:
1) Heating time of steel billet: in order to reduce the adverse effect of sulfur on the rolling process, the billet is heated sufficiently to facilitate the formation of manganese sulfide from sulfur and manganese.
2) The heating temperature is controlled.
3) Cooling, heat preservation and temperature raising: the temperature reduction and heat preservation system of the low-carbon high-sulfur free-cutting steel cannot be executed when the temperature is reduced, heat preservation and temperature raising of the low-carbon high-sulfur free-cutting steel cannot be executed, when rolling is stopped due to roll changing, post faults, equipment faults and the like of a rolling mill, the heating furnace executes the temperature reduction and heat preservation system of the low-carbon high-sulfur free-cutting steel on the basis of the actual temperature of each section according to the length of the rolling time, and the time for heating in advance is selected according to the length of the rolling time when the temperature is raised.
4) And (3) smoke residual oxygen control: in order to reduce the grain boundary oxidation phenomenon, the residual oxygen content of the flue gas is controlled to be less than 6%; the residual oxygen content of the flue gas is less than 8 percent when the heat preservation and rolling stop are carried out.
5) And (3) controlling the temperature of the rolled steel: the temperature of the steel is controlled to be uniform, and the temperature difference between the temperature of the watermark of the steel billet and the temperature of other positions is less than or equal to 20 ℃.
6) Pass reduction control: the rough rolling is a three-roller rolling mill, the rolling piece is smoothly sent out of the hole pattern to finish rolling by single-pass rolling, and when the friction force is smaller than the running resistance of the rolling piece, the rolling piece can slip in the hole pattern and cannot normally walk to cause a hole pattern steel clamping accident by virtue of the friction force between the hole pattern and the rolling piece and the rotation of the roller. This is particularly true when the first stand is rough rolled. Because the first frame rough rolling has short rolled piece, large absolute rolling reduction and small roller conveying force, even after the first frame rough rolling is meshed with the hole, the roller does not contact with the rolled piece to lose conveying force, the running resistance is large, the conveying force is small, and the first frame rough rolling reduction is strictly controlled. The reduction rate of the rough rolling single pass is controlled to be 15-25%.
7) Edge temperature drop control: in order to reduce the temperature drop condition of the edge part in the rolling process, a heat preservation cover is covered on a roller way before rough rolling and continuous rolling; in order to reduce temperature drop caused by flushing cooling water of a continuous rolling mill to the surface of a rolled piece, a cooling water baffle is added at an inlet and an outlet of the continuous rolling mill; the continuous rolling stops the cooling water between machines; and under the condition of ensuring the cooling of the roller, the temperature drop of the cooling water of the rolling mill on the rolled piece is reduced.
8) And (3) final rolling temperature control: the low-carbon high-sulfur free-cutting steel has poor plasticity along with the reduction of the temperature of the steel, and the maximum hot brittleness and the worst plasticity at about 950 ℃, so that the finishing temperature is controlled to be more than or equal to 980 ℃, and the edge cracking of the finished product is effectively controlled.
Preferably, the step 3) of cooling, heat preservation and temperature raising according to the length of the rolling stop time comprises the following steps: when the rolling is stopped for less than 0.25 hour, the furnace temperature of the soaking section is kept not to be reduced, and the furnace temperature of the heating section is reduced by 30-50 ℃; when stopping rolling for 0.25-0.5 hour, the temperature of the soaking section furnace is reduced by 10-30 ℃, the temperature of the heating section furnace is reduced by 50-100 ℃, and the initial rolling is advanced for 5-10 minutes; when stopping rolling for 0.5-1 hour, the temperature of the soaking section furnace is reduced by 30-50 ℃, the temperature of the heating section furnace is reduced by 100-150 ℃, and the initial rolling is advanced for 10-20 minutes; when stopping rolling for 1-1.5 hours, the temperature of the soaking section furnace is reduced by 50-150 ℃, the temperature of the heating section furnace is reduced by 150-200 ℃, and the initial rolling is advanced for 20-30 minutes; when the rolling is stopped for more than 1.5 hours, the temperature of the soaking section furnace is reduced to 850-1000 ℃, the temperature of the heating section furnace is reduced to 850-1000 ℃, and the initial rolling is advanced to raise the temperature for 60-90 minutes.
Preferably, the specific temperature control step of the step 2) is as follows: the heating temperature of the soaking section is 1200+/-20 ℃, the heating temperature of the upper heating section is 1200+/-20 ℃, the heating temperature of the lower heating section 11 is 1240+/-20 ℃, the heating temperature of the lower heating section 12 is 1260+/-20 ℃, the heating temperature of the lower heating section 2 is 1120+/-20 ℃, and the heating temperature of the preheating section is 650+/-100 ℃
Preferably, the heating time of the step 1) is 4.0±0.5 hours.
Preferably, the initial rolling temperature in the step 5) is 1100-1140 ℃, so as to ensure that the final rolling temperature meets the requirement, reduce the low-temperature head-forming layering phenomenon in the rough rolling process, control the lower limit of the initial rolling temperature, and simultaneously, define the upper limit of the initial rolling temperature in order to avoid hole type slip caused by high rolling temperature and small friction coefficient.
Preferably, the first pass reduction of step 6) is not more than 20%.
Preferably, the water temperature of the cooling water of the rolling mill in the step 7) is controlled to be 35-40 ℃.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages: after the low-carbon high-sulfur free-cutting steel heating process and the rolling process control method are implemented, the problems of hole type slip steel clamping, head separation, finished product edge cracking and the like can be effectively prevented, and the phenomena of rolling mill hole type slip steel clamping and rolling cracking in the production process are avoided.
Drawings
FIG. 1 is a schematic diagram of temperature measuring points of each section of a heating furnace;
fig. 2 is a schematic diagram of temperature measuring points of the lower heating section 11 and the lower heating section 12 of the heating furnace.
Detailed Description
The technical scheme of the invention is further described below with reference to specific embodiments.
As shown in FIGS. 1 and 2, the heat equalizing section, the 2-upper heating section, the 3-lower heating section, the 31-lower heating section 12, the 32-lower heating section 11 (mill direction), the 4-lower heating section 2, 5-preheating section are shown in the drawing.
Example 1
A hot rolling process of low-carbon high-sulfur free-cutting narrow strip steel comprises the following steps:
1) Heating time of steel billet: fully heating the steel billet for 3.6 hours;
2) Controlling the heating temperature;
3) Cooling, heat preservation and temperature raising: when the rolling mill is stopped due to roll replacement, post faults, equipment faults and the like, the heating furnace executes a heat-preserving system of the low-carbon high-sulfur free-cutting steel according to the length of the rolling stopping time on the basis of the actual temperature of each section, and the time for heating is selected in advance according to the length of the rolling stopping time when the temperature is increased; the soaking temperature is controlled to be 1210 ℃, the upper heating section 1215 ℃, the lower heating section 11 is 1255 ℃, the lower heating section 12 is 1276 ℃, the lower heating section 2 is 1128 ℃, and the preheating section is 655 ℃.
4) And (3) smoke residual oxygen control: controlling the residual oxygen content of the flue gas to be 3.5%;
5) And (3) controlling the temperature of the rolled steel: the initial rolling temperature of rough rolling is 1135 ℃, and the steel temperature is controlled to be uniform;
6) Pass reduction control: controlling the first pass reduction rate of rough rolling to 18.0%, the second pass reduction rate to 22.8% and the third pass reduction rate to 21.1%;
7) Edge temperature drop control: the roller way is covered with a heat preservation cover before rough rolling and continuous rolling, and a cooling water baffle is added at the inlet and outlet of a continuous rolling plain rolling mill; the continuous rolling stops the cooling water between machines; under the condition of ensuring the cooling of the roller, reducing the temperature drop of the cooling water of the rolling mill on the rolled piece;
8) And (3) final rolling temperature control: the final rolling temperature is controlled to 1015 ℃, and the cracking of the edge of the finished product is effectively controlled.
The number of the materials fed in this example, the hole type slip clip steel and the number of the edge cracking of the finished product are shown in Table 3.
Example 2
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 3
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 4
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 5
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 6
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 7
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 8
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 9
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
Example 10
The low-carbon high-sulfur free-cutting narrow strip steel hot rolling process is the same as that of example 1, and the specific heating time, the temperature of the soaking section, the upper heating section, the lower heating section 11, the lower heating section 12, the lower heating section 2 and the preheating section and the residual oxygen content of flue gas are shown in table 1. The start rolling temperature, finish rolling temperature and reduction per pass of rough rolling are shown in Table 2. The number of the materials fed is shown in Table 3, and the number of the hole type slip clip steel and the number of the edge cracks of the finished product are shown in Table 3.
TABLE 1 heating temperature, heating time and residual oxygen content of the examples
TABLE 2 initial rolling temperature, final rolling temperature and first frame rough rolling stock size for each example
TABLE 3 batch counts for each example, hole-type slip steel and finished edge cracking counts
Claims (5)
1. The hot rolling process of the low-carbon high-sulfur free-cutting narrow strip steel is characterized by comprising the following steps of:
1) Heating time of steel billet: fully heating the steel billet;
2) The heating temperature is controlled, the heating temperature of the soaking section is 1200+/-20 ℃, the heating temperature of the upper heating section is 1200+/-20 ℃, the heating temperature of the lower heating section 11 is 1240+/-20 ℃, the heating temperature of the lower heating section 12 is 1260+/-20 ℃, the heating temperature of the lower heating section 2 is 1120+/-20 ℃, and the heating temperature of the preheating section is 650+/-100 ℃;
3) Cooling, heat preservation and temperature raising: when the rolling mill is stopped due to roll replacement, post faults, equipment faults and the like, the heating furnace executes a heat-preserving system of the low-carbon high-sulfur free-cutting steel according to the length of the rolling stopping time on the basis of the actual temperature of each section, and the time for heating is selected in advance according to the length of the rolling stopping time when the temperature is increased; the method comprises the following specific steps: when the rolling is stopped for less than 0.25 hour, the furnace temperature of the soaking section is kept not to be reduced, and the furnace temperature of the heating section is reduced by 30-50 ℃; when stopping rolling for 0.25-0.5 hour, the temperature of the soaking section furnace is reduced by 10-30 ℃, the temperature of the heating section furnace is reduced by 50-100 ℃, and the initial rolling is advanced for 5-10 minutes; when stopping rolling for 0.5-1 hour, the temperature of the soaking section furnace is reduced by 30-50 ℃, the temperature of the heating section furnace is reduced by 100-150 ℃, and the initial rolling is advanced for 10-20 minutes; when stopping rolling for 1-1.5 hours, the temperature of the soaking section furnace is reduced by 50-150 ℃, the temperature of the heating section furnace is reduced by 150-200 ℃, and the initial rolling is advanced for 20-30 minutes; when stopping rolling for more than 1.5 hours, the temperature of the soaking section furnace is reduced to 850-1000 ℃, the temperature of the heating section furnace is reduced to 850-1000 ℃, and the initial rolling is advanced to raise the temperature for 60-90 minutes;
4) And (3) smoke residual oxygen control: controlling the residual oxygen content of the flue gas to be less than 6%; the residual oxygen content of the flue gas is less than 8 percent when the heat preservation and rolling stop are carried out;
5) And (3) controlling the temperature of the rolled steel: the steel temperature is controlled to be uniform, and the temperature difference between the temperature of the watermark of the steel billet and the temperature of other positions is less than or equal to 20 ℃;
6) Pass reduction control: controlling the single pass reduction rate of rough rolling to 15-25%;
7) Edge temperature drop control: the roller way is covered with a heat preservation cover before rough rolling and continuous rolling, and a cooling water baffle is added at the inlet and outlet of a continuous rolling plain rolling mill; the continuous rolling stops the cooling water between machines; under the condition of ensuring the cooling of the roller, reducing the temperature drop of the cooling water of the rolling mill on the rolled piece;
8) And (3) final rolling temperature control: the final rolling temperature is controlled to be more than or equal to 980 ℃, and the cracking of the edge part of the finished product is effectively controlled.
2. The hot rolling process for low carbon high sulfur free cutting strip steel as claimed in claim 1, wherein the heating time of step 1) is 4.0±0.5 hours.
3. The hot rolling process for low carbon high sulfur free cutting strip steel as claimed in claim 1 wherein the initial rolling temperature of step 5) is 1100-1140 ℃.
4. The hot rolling process for low carbon high sulfur free cutting strip steel as claimed in claim 1 wherein the first pass reduction of step 6) is not more than 20%.
5. The hot rolling process for low carbon high sulfur free cutting strip steel as claimed in claim 1, wherein the water temperature of the rolling mill cooling water of step 7) is controlled to be 35-40 ℃.
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| CN104451458A (en) * | 2014-12-01 | 2015-03-25 | 杭州钢铁集团公司 | Free-cutting steel and production method thereof and application of free-cutting steel in manufacturing keys |
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| JPH08174008A (en) * | 1994-12-21 | 1996-07-09 | Sumitomo Metal Ind Ltd | Hot rolling method of high s free-cutting stainless steel |
| JP2001137908A (en) * | 1999-11-05 | 2001-05-22 | Nippon Koshuha Steel Co Ltd | Hot-rolling method of high sulfur free-cutting stainless steel |
| CN1608758A (en) * | 2004-11-22 | 2005-04-27 | 宝钢集团上海五钢有限公司 | Hot continuous rolling process of high-sulfur (sulfur-phosphorus) free cutting structural steel |
| CN101418422A (en) * | 2008-07-29 | 2009-04-29 | 湖南华菱湘潭钢铁有限公司 | Free-cutting steel and method for producing the same |
| CN104451458A (en) * | 2014-12-01 | 2015-03-25 | 杭州钢铁集团公司 | Free-cutting steel and production method thereof and application of free-cutting steel in manufacturing keys |
| CN110396649A (en) * | 2019-07-17 | 2019-11-01 | 南京钢铁股份有限公司 | A kind of control production method of the low-carbon sulphur automatic steel with hot-rolling edge cracking |
| CN112404126A (en) * | 2020-10-29 | 2021-02-26 | 中天钢铁集团有限公司 | Controlled rolling and cooling method for improving sulfide form of free-cutting steel wire rod |
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